^ The step/platform would tend to limit his movement prior to taking off (leaving the ground). Not sure if that is the intention of the exercise. There is undoubtely a plyometric aspect to serving from the step platform. In plyometrics exercises, athletes often step or jump from a box followed immediately by a sprint. In this case, Roger lands after his serve jump and then immediately runs forward, split steps and moves again. All-in-all a pretty good way to develop foot speed/leg power.

^ The step/platform would tend to limit his movement prior to taking off (leaving the ground). Not sure if that is the intention of the exercise. There is undoubtely a plyometric aspect to serving from the step platform. In plyometrics exercises, athletes often step or jump from a box followed immediately by a sprint. In this case, Roger lands after his serve jump and then immediately runs forward, split steps and moves again. All-in-all a pretty good way to develop foot speed/leg power.

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I'm also thinking that the step may be used to shorten the reaction time from the return. Since he's higher up, it'll take longer for him to get down and then hit his first shot following his opponent's return. This added height might force him to split step and prep for his first shot faster.